[Dailydrool] plaque on teeth

[Shirley Grange]

My 5 year old Zinnia has had her teeth scraped twice (under anesthetic) and now they are so full of
plaque that the vet wants to do it again (after less than a year).  They really do look awful.  I tried brushing them, but Zinnia
didn't cooperate much and it's hard to get to those back teeth.  So the vet has now sold me Biotene
Drinking Water Additive, 4 measily oz. for $25!!  Do any of you Droolers have a solution for keeping 
the plaque off??  Is there a home remedy or something to add to the water?  Does it have to do with
the pH of the water?  Thanks for any wisdom you can impart!
Shirley + George in Maine, and the hounds Roscoe + Zinnia